Protective coatings for materials exposed to corrosive, hostile, or chemically interfering environments have primarily been of the type that provide an impervious barrier to all components of the environment to which such coated materials are exposed. The substrate materials include, for example, metals, metal oxides, and polymers of various types. A particular disadvantage of such protective coatings arises when the coatings are no longer impervious. Additionally, the compatibility of the coating and the respective substrate may be lacking in that the coating fails to adhere to the substrate either immediately upon application thereto or upon ceasing to be impervious.
Thus, there exists a need for a protective coating which does not rely on being totally impervious to the environment into which the substrate is placed and which adheres well to the substrate upon which it is applied. Furthermore, there exists a need for a protective coating for passive metals and alloys containing same which are subject to localized corrosion via anionic attack.